Program to update list items by their absolute values in Python

Sometimes we need to convert negative numbers in a list to their absolute values while keeping positive numbers unchanged. Python provides several approaches to update list items with their absolute values.

Using map() with Lambda Function

The map() function applies a lambda function to each element in the list ?

def solve(nums):
    return list(map(lambda x: abs(x), nums))

nums = [5, -7, -6, 4, 6, -9, 3, -6, -2]
result = solve(nums)
print("Original list:", nums)
print("Absolute values:", result)

Original list: [5, -7, -6, 4, 6, -9, 3, -6, -2]
Absolute values: [5, 7, 6, 4, 6, 9, 3, 6, 2]

Using List Comprehension

List comprehension provides a more Pythonic and readable approach ?

nums = [5, -7, -6, 4, 6, -9, 3, -6, -2]
result = [abs(x) for x in nums]
print("Original list:", nums)
print("Absolute values:", result)

Original list: [5, -7, -6, 4, 6, -9, 3, -6, -2]
Absolute values: [5, 7, 6, 4, 6, 9, 3, 6, 2]

In-Place Update Using enumerate()

To modify the original list without creating a new one, use enumerate() ?

nums = [5, -7, -6, 4, 6, -9, 3, -6, -2]
print("Before update:", nums)

for i, value in enumerate(nums):
    nums[i] = abs(value)

print("After update:", nums)

Before update: [5, -7, -6, 4, 6, -9, 3, -6, -2]
After update: [5, 7, 6, 4, 6, 9, 3, 6, 2]

Comparison

Conclusion

Use list comprehension for the most readable and Pythonic solution. Choose enumerate() for in-place updates when memory efficiency is important. The map() approach works well in functional programming contexts.